Self-assembled pattern process for fabricating magnetic junctions usable in spin transfer torque applications

ABSTRACT

Magnetic junctions usable in a magnetic device and a method for providing the magnetic junctions are described. A patterned seed layer is provided. The patterned seed layer includes magnetic seed islands interspersed with an insulating matrix. At least a portion of the magnetoresistive stack is provided after the patterned seed layer. The magnetoresistive stack includes at least one magnetic segregating layer. The magnetic segregating layer(s) include at least one magnetic material and at least one insulator. The method anneals the at least the portion of the magnetoresistive stack such that the at least one magnetic segregating layer segregates. The constituents of the magnetic segregating layer segregate such that portions of magnetic material(s) align with the magnetic seed islands(s) and such that portions of the insulator(s) align with the insulating matrix.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of provisional Patent ApplicationSer. No. 62/512,656, filed May 30, 2017, entitled SELF-ASSEMBLEDPATTERNING PROCESS FOR MAGNETIC DEVICES SUCH AS SPIN TRANSFER TORQUEMAGNETIC RANDOM ACCESS MEMORIES, assigned to the assignee of the presentapplication, and incorporated herein by reference.

BACKGROUND OF THE INVENTION

Magnetic memories, particularly magnetic random access memories (MRAMs),have drawn increasing interest due to their potential for highread/write speed, excellent endurance, non-volatility and low powerconsumption during operation. An MRAM can store information utilizingmagnetic materials as an information recording medium. One type of MRAMis a spin transfer torque random access memory (STT-MRAM). STT-MRAMutilizes magnetic junctions written at least in part by a current driventhrough the magnetic junction.

A conventional magnetic tunneling junction (MTJ) may be used in aconventional STT-MRAM. The MTJ includes a pinned layer, a free layer anda tunneling barrier layer between the pinned and free layers. The MTJtypically resides on a substrate and may include seed and cappinglayer(s) as well as an antiferromagnetic (AFM) pinning layer adjoiningthe pinned layer. A bottom contact below the MTJ and a top contact onthe MTJ may be used to drive current through the MTJ in acurrent-perpendicular-to-plane (CPP) direction.

The pinned layer and the free layer are magnetic. The magnetization ofthe pinned layer is fixed, or pinned, in a particular direction. Thefree layer has a changeable magnetization. The free layer and the pinnedlayer may each be a single layer or include multiple layers. The pinnedlayer and free layer may have their magnetizations orientedperpendicular to the plane of the layers (perpendicular-to-plane) or inthe plane of the layers (in-plane).

To switch the magnetization of the conventional free layer, a current isdriven perpendicular to plane. The current becomes spin polarized andexerts a spin torque on the magnetic moment of the free layer. When asufficient current is driven from the top contact to the bottom contact,the magnetization of the conventional free layer may switch to beparallel to the magnetization of a conventional bottom pinned layer.When a sufficient current is driven from the bottom contact to the topcontact, the magnetization of the free layer may switch to beantiparallel to that of the bottom pinned layer. The differences inmagnetic configurations correspond to different magnetoresistances andthus different logical states (e.g. a logical “0” and a logical “1”) ofthe conventional MTJ.

To fabricate conventional MTJs in a STT-MRAM, the layers in the MTJ areblanket deposited across the surface of the substrate. These layers forman MTJ stack. Layers for the pinned layer, the nonmagnetic spacer layerand the free layer are all included in the MTJ stack. Additional layerssuch as seed and/or capping layers may also be part of the MTJ stack.Once the entire MTJ stack is deposited, a mask is provided. The maskcovers the regions where the MTJs are to be formed and has aperturesbetween the MTJs. The exposed portions of the MTJ stack are thenremoved. This removal may be accomplished via processes such as reactiveion etches (RIEs) and/or ion milling. Thus, the individual MTJs aredefined from the MTJ stack. Fabrication of the STT-MRAM may then becompleted. For example, insulating refill, conductive lines, and othercomponents maybe formed.

High density STT-MRAM devices are increasingly desired. The spacingbetween memory cells and, therefore, the conventional MTJs continues toshrink. The height of the MTJ stack does not necessarily decrease withthe reduction in spacing. Consequently, the aspect ratio (height dividedby width or height divided by length) may increase. As the spacingbetween MTJs decreases and the aspect ratio increases, fabrication maybecome more challenging. For example, ion milling may be incapable ofdefining the MTJs at smaller spacing and higher aspect ratios. Further,because the MTJs have multiple layers of various materials, no singleRIE chemistry is currently available for fabrication. Accordingly, whatis needed is a method and system that may improve fabrication of spintransfer torque based memories. The method and system described hereinaddress such a need.

BRIEF SUMMARY OF THE INVENTION

Magnetic junctions usable in a magnetic device and a method forproviding the magnetic junctions are described. A patterned seed layeris provided. The patterned seed layer includes magnetic seed islandsinterspersed with an insulating matrix. Magnetic seed islands may bemagnetic or nonmagnetic. A magnetic seed island is a seed structure fora magnetic structure. At least a portion of the magnetoresistive stackis provided after the patterned seed layer. The portion of themagnetoresistive stack includes at least one magnetic segregating layer.The magnetic segregating layer(s) include at least one magnetic materialand at least one insulator. The method anneals at least the portion ofthe magnetoresistive stack such that the at least one magneticsegregating layer segregates. The constituents of the magneticsegregating layer segregate such that portions of magnetic material(s)align with the magnetic seed islands(s) and such that portions of theinsulator(s) align with the insulating matrix.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a flow chart depicting an exemplary embodiment of a method forproviding self-assembled magnetic junctions usable in magnetic devicessuch as a magnetic memory programmable using spin transfer torque.

FIGS. 2-5 depict an exemplary embodiment of self-assembled magneticjunctions during fabrication.

FIG. 6 is a flow chart depicting an exemplary embodiment of a method forproviding self-assembled magnetic junctions usable in magnetic devicessuch as a magnetic memory programmable using spin transfer torque.

FIGS. 7-11 depict an exemplary embodiment of self-assembled magneticjunctions during fabrication.

FIGS. 12-13 depict an exemplary embodiment of self-assembled magneticjunctions during fabrication.

FIG. 14 is a flow chart depicting another exemplary embodiment of amethod for providing self-assembled magnetic junctions usable inmagnetic devices such as a magnetic memory programmable using spintransfer torque.

FIGS. 15-17 depict an exemplary embodiment of self-assembled magneticjunctions during fabrication.

FIGS. 18-19 depict another exemplary embodiment of self-assembledmagnetic junctions during fabrication.

FIGS. 20-21 depict another exemplary embodiment of self-assembledmagnetic junctions during fabrication.

FIG. 22 depicts an exemplary embodiment of a memory utilizing magneticjunctions in the memory element(s) of the storage cell(s).

DETAILED DESCRIPTION OF THE INVENTION

The exemplary embodiments relate to magnetic junctions usable inmagnetic devices, such as magnetic memories, and the devices using suchmagnetic junctions. The magnetic memories may include spin transfertorque magnetic random access memories (STT-MRAMs) and may be used inelectronic devices employing nonvolatile memory. Such electronic devicesinclude but are not limited to cellular phones, smart phones, tables,laptops and other portable and non-portable computing devices. Thefollowing description is presented to enable one of ordinary skill inthe art to make and use the invention and is provided in the context ofa patent application and its requirements. Various modifications to theexemplary embodiments and the generic principles and features describedherein will be readily apparent. The exemplary embodiments are mainlydescribed in terms of particular methods and systems provided inparticular implementations. However, the methods and systems willoperate effectively in other implementations. Phrases such as “exemplaryembodiment”, “one embodiment” and “another embodiment” may refer to thesame or different embodiments as well as to multiple embodiments. Theembodiments will be described with respect to systems and/or deviceshaving certain components. However, the systems and/or devices mayinclude more or fewer components than those shown, and variations in thearrangement and type of the components may be made without departingfrom the scope of the invention. The exemplary embodiments will also bedescribed in the context of particular methods having certain steps.However, the method and system operate effectively for other methodshaving different and/or additional steps and steps in different ordersthat are not inconsistent with the exemplary embodiments. Thus, thepresent invention is not intended to be limited to the embodimentsshown, but is to be accorded the widest scope consistent with theprinciples and features described herein.

Magnetic junctions usable in a magnetic device and a method forproviding the magnetic junctions are described. A patterned seed layeris provided. The patterned seed layer includes magnetic seed islandsinterspersed with an insulating matrix. Magnetic seed islands may bemagnetic or nonmagnetic. A magnetic seed island is a seed structure fora magnetic structure. At least a portion of the magnetoresistive stackis provided after the patterned seed layer. This portion of themagnetoresistive stack includes at least one magnetic segregating layer.The magnetic segregating layer(s) include at least one magnetic materialand at least one insulator. The method anneals the at least the portionof the magnetoresistive stack such that the at least one magneticsegregating layer segregates. The constituents of the magneticsegregating layer segregate such that portions of magnetic material(s)align with the magnetic seed islands(s) and such that portions of theinsulator(s) align with the insulating matrix.

The exemplary embodiments are described in the context of particularmethods, magnetic junctions and magnetic memories having certaincomponents. One of ordinary skill in the art will readily recognize thatthe present invention is consistent with the use of magnetic junctionsand magnetic memories having other and/or additional components and/orother features not inconsistent with the present invention. The methodand system are also described in the context of current understanding ofthe spin transfer phenomenon, of magnetic anisotropy, crystallization,segregation of immiscible materials and other physical phenomenon.Consequently, one of ordinary skill in the art will readily recognizethat theoretical explanations of the behavior of the method and systemare made based upon this current understanding. However, the method andsystem described herein are not dependent upon a particular physicalexplanation. One of ordinary skill in the art will also readilyrecognize that the method and system are described in the context of astructure having a particular relationship to the substrate. However,one of ordinary skill in the art will readily recognize that the methodand system are consistent with other structures. In addition, the methodand system are described in the context of certain layers beingsynthetic and/or simple. However, one of ordinary skill in the art willreadily recognize that the layers could have another structure.Furthermore, the method and system are described in the context ofmagnetic junctions and/or substructures having particular layers.However, one of ordinary skill in the art will readily recognize thatmagnetic junctions and/or substructures having additional and/ordifferent layers not inconsistent with the method and system could alsobe used. Moreover, certain components are described as being magnetic,ferromagnetic, and ferrimagnetic. As used herein, the term magneticcould include ferromagnetic, ferrimagnetic or like structures. Thus, asused herein, the term “magnetic” or “ferromagnetic” includes, but is notlimited to ferromagnets and ferrimagnets. As used herein, “in-plane” issubstantially within or parallel to the plane of one or more of thelayers of a magnetic junction. Conversely, “perpendicular” and“perpendicular-to-plane” corresponds to a direction that issubstantially perpendicular to one or more of the layers of the magneticjunction.

FIG. 1 is a flow chart depicting an exemplary embodiment of a method 100for providing self-assembled magnetic junctions programmable using spintransfer torque. The magnetic junctions provided may be usable inmagnetic devices such as a STT-MRAM and, therefore, in a variety ofelectronic devices. Each of the magnetic junctions formed using themethod 100 includes at least a free layer having a changeable magneticmoment, a pinned layer and a nonmagnetic spacer layer such as acrystalline MgO layer. The free and/or pinned layers of the magneticjunction may have a high perpendicular magnetic anisotropy (PMA). Stateddifferently, the perpendicular magnetic anisotropy energy may exceed theout-of-plane demagnetization energy. FIGS. 2-5 depict side views of anexemplary embodiment of a magnetic device 200 during fabrication usingthe method 100. In some embodiments, the magnetic device 200 is anSTT-MRAM. FIGS. 2-5 are not to scale and only structures that may be ofinterest are separately labeled and included. Referring to FIGS. 1-5,the method 100 is described in the context of the magnetic device 200.However, other magnetic devices including other magnetic junction(s) maybe formed. Further, the method 100 may start after other steps informing the magnetic device 200 have been performed. For example,selection transistor(s), contacts, or other components may have beenfabricated. For simplicity, some steps may be omitted, performed inanother order, include substeps and/or combined.

A patterned seed layer is provided, via step 102. The patterned seedlayer includes magnetic seed islands interspersed with an insulator.Magnetic seed islands may be magnetic or nonmagnetic. A magnetic seedisland is so named because a magnetic seed island is a seed layer for asubsequent magnetic structure, such as the magnetic segregating layer(s)described below. The magnetic seed islands may be conductive (e.g.metallic). The insulator may be considered to form an insulating matrixthat surrounds each of the magnetic seed islands. Step 102 may includedepositing a seed layer for the magnetic junction to be provided,patterning the seed layer photolithographically to form the magneticseed islands using a mask and depositing an insulating layer. Portionsof the insulating layer might be removed prior to the mask beingremoved. Alternatively, the mask may be removed without a separateinsulator removal step. Removal of the mask may remove excess insulatinglayer, leaving the insulating matrix and magnetic seed islands.Alternatively, the insulating layer may be deposited. A mask may coverthe portions of the insulating layer that are to form the insulatingmatrix. The exposed portions of the insulating layer are removed. Theseed layer for the magnetic junctions may then be deposited. Some of theseed layer may be etched prior to removal of the mask. Alternatively,the mask may simply be removed. Removal of the mask may remove excessseed layer. In either process, magnetic seed islands in the insulatingmatrix remain. In other embodiments, other methods may be used to formthe patterned seed layer.

FIG. 2 depicts the magnetic device 200 after step 102 has beenperformed. The patterned seed layer 210 has been provided on thesubstrate 201. The seed layer 210 includes magnetic seed islands 214interspersed with an insulating matrix 212. Although only one dimensionin-plane is shown (e.g. left to right), the patterned seed layer 210 istypically patterned in two dimensions. Thus, the length and width of themagnetic seed islands 214 as well as the distance between the islands(e.g. the length of the insulating matrix 212) are provided as part ofstep 102. In some embodiments, each magnetic seed island 214 correspondsto a single magnetic junction. In other embodiments, the seed island 214may correspond to multiple magnetic junctions. For example, the seedisland 214 may extend across multiple magnetic junctions in thedirection out of the plane of the page if a single pinned layer isdesired to be used for multiple magnetic junctions. In at least someembodiments, the shape of the footprint of the magnetic seed islands 214corresponds to the footprint of the pinned or other magnetic layer(s)that will be adjacent to the magnetic seed islands 214. The desireddimensions of the magnetic seed islands 214 may differ for perpendicularand in-plane junctions. For perpendicular designs, the magnetic seedislands may have a circular footprint with a diameter as small as fivenanometers and as large as one hundred nanometers. For in-plane magneticjunctions, the magnetic seed island may be elongated (e.g. elliptical)with short axis of at least ten nanometers and not more than one hundrednanometers and a long axis of at least twenty nanometers and not morethan four hundred nanometers. However, other shapes (footprints) and/orsizes are possible. For example, a square and/or rectangular footprintmay be used. Examples of materials that may be used for the magneticseed islands 214 include but may not be limited to CrV, NiTa, RuAl, TiNand/or CrTi alloys.

The insulating matrix 212 may be an insulating material that enablessegregation of the magnetic material and insulator of the magneticsegregating layer (described below) based on the seed layer. Oxides aswell as Nitrides and oxynitride of various materials might be used. Forexample, materials such as AlO, AlN, SiO, SiN, MgO, MgN and/or TiO maybe used. In some embodiments, the insulating matrix 212 may be siliconoxide or nitride, such as SiO₂ or Si₃N₄. In another embodiment, theinsulating matrix 212 may be another oxide including but not limited toaluminum oxide. The insulating matrix 212 may be used to electricallyisolate the magnetic junctions being formed. Thus, the insulating matrix212 may surround the sides of some or all of the magnetic seed islands214.

A first portion of a magnetoresistive stack is provided, via step 104.The magnetoresistive stack includes one or more layers for the magneticjunction, but has not been patterned into individual magneticjunction(s). Thus, step 104 includes depositing one or more layers thatwill become part of the magnetic junction(s). At least one magneticsegregating layer is provided as part of step 104. A magneticsegregating layer includes at least one magnetic material and at leastone insulator. The magnetic material(s) and insulator(s) are immiscible.Thus, step 104 may include sputtering or otherwise depositing thesematerials such that the resulting film is metastable. In someembodiments, only the magnetic segregating layer is deposited. In otherembodiments additional layers might be deposited. For example, thenonmagnetic spacer layer may be provided as part of step 104. An MgOtunneling barrier layer may, therefore, be provided as part of step 104.The MgO deposited may not be fully crystallized until one or moreanneals are performed, as discussed below. In some such embodiments, thematerial(s) for a free layer may be deposited. For example, anadditional magnetic segregating layer may be deposited on thenonmagnetic spacer layer. This additional magnetic segregating layer mayform the free layer. If a dual magnetic junction is to be provided, anadditional nonmagnetic spacer layer and another magnetic segregatinglayer may also be deposited. Other layers such as polarizationenhancement layers (PELs), coupling layers and antiferromagnetic (AFM)or other pinning layers and/or other layers that are to bephotolithographically defined may be deposited at a later time. Further,although only a single magnetic segregating layer is described for eachdeposition above, in other embodiments, multiple magnetic segregatinglayers may be provided at each location.

FIG. 3 depicts the magnetic device 200 after step 104 is performed.Thus, a portion of the magnetoresistive stack 220 has been formed. Amagnetic segregating layer 222 has been deposited on the patterned seedlayer 210. the magnetic segregating layer 222 may be desired to share aninterface with at least the magnetic seed islands 214. In someembodiments, the magnetic segregating layer 222 shares an interface withthe patterned seed layer 210. Although shown as a single layer, themagnetic segregating layer 222 may include multiple sublayers. Forexample, the magnetic segregating layer 222 may include a multilayer ofthin layer(s) of the magnetic material(s) alternating with thin layer(s)of the insulator. However, in general, the magnetic material(s) andinsulator(s) are desired to be intermixed due to the deposition process.For example, small particles of the magnetic material(s) mayinterspersed in a matrix formed of the insulator.

The magnetic segregating layer 222 may include FePt and/or CoPt as themagnetic material(s). Other magnetic materials that may segregate fromthe insulator, such as CoFeB, might also be used. The insulator mayinclude silicon oxide, such as SiO₂, and/or aluminum oxide. Other oxidessuch as B2O3, AIN and/or MgO might also be used. In general, magneticmaterials and oxides/insulators used are those that both provide thedesired properties for the magnetic junction and are capable ofsegregating from each other based upon the seed islands 214 andinsulating matrix 212. The stoichiometry of the magnetic segregatinglayer 222 may depend upon the size of the magnetic junctions in theplane perpendicular to the side view shown as well as the distancedesired between the magnetic junctions. For example, a larger fractionof the magnetic segregating layer 222 may be the magnetic material(s) ifmagnetic junctions having larger footprints are desired. In someembodiments, the desired distance between magnetic junctions may affectthe fraction of the insulator provided. For example, if the magneticjunctions are desired to be more distant in-plane, then a higherfraction of insulator may be provided as part of the magneticsegregating layer. A combination of the magnetic seed island 214dimensions/separation (size of insulating matrix 212) and the properratio of magnetic material(s) to insulator(s) is used to achieve uniformsize distribution and magnetic properties. One example volume fractionof insulator is ten volume percent through fifty volume percent (i.e.ninety through fifty volume percent magnetic material(s)).

Also shown in FIG. 3 is an optional additional portion 224 of themagnetoresistive stack 220. In some embodiments, the additional portion224 of the magnetoresistive stack may include a tunneling barrier layer,layer(s) for the free layer, or other layers. If some or all of the freelayer is part of the layer 224, then this portion of the free layer mayinclude additional magnetic segregating layer(s). In other embodiments,the portion 224 may be omitted.

The portions of the magnetoresistive stack 220 that has been provided isannealed such that constituents of the magnetic segregating layer(s) 224segregate, via step 106. The anneal may be accomplished via blockheating (wafer in place on a heated chuck) or via a rapid thermal anneal(RTA) in various embodiments. The anneal temperature may be at least twohundred degrees Celsius and not more than seven hundred degrees Celsiusin some embodiments. However, other times and/or temperatures arepossible. Further, other anneal processes may be used. The magneticmaterial(s) in the magnetic segregating layer 224 separate from theinsulator. The magnetic material(s) thus tend to form islands. Becauseof the presence of the magnetic seed islands 214, the magneticmaterial(s) tend to align with and share at least part of an interfacewith the magnetic seed islands 214. The magnetic materials may also beclose in dimension and footprint shape to the magnetic seed islands 214.Similarly, the insulator tends to align with the insulating matrix 212.

FIG. 4 depicts the magnetic device 200 after step 106 has beenperformed. Thus, the magnetic segregating layer 222 has separated intomagnetic layers 226 and insulator layers 228 that are aligned with themagnetic seed islands 214 and insulating matrix 212, respectively. Themagnetic layers 226 may but need not be centered over the magnetic seedislands 214 and may but need not be the same size as the islands 214.Similarly, the insulating layers 228 may but need not be centered overthe insulating matrix 212 and may but need not be the same size as theinsulating matrix 212. As used herein, a layer aligned with anotherlayer overlaps the other layer by at least fifty percent. In someembodiments, a layer being aligned with another layer means that thereis no cross-over between seed island and adjacent magnetic island.Although the magnetic layers 226 are shown as larger than the magneticseed islands 214, the dimensions of the magnetic seed islands 214 can beeither smaller or larger than the dimensions of the magnetic layers 226.Thus, the magnetic seed islands 214 may be smaller or larger than thedesired footprint of the magnetic junction being formed. The choice isdetermined by segregation properties of the magnetic material(s) in themagnetic layers 226 as well as magnetic properties (such asperpendicular anisotropy) dependency of growth on metal (the magneticseed islands 214) or insulator material 212. Thus, each magnetic layer226 is aligned with a magnetic seed island 214. Similarly, eachinsulator layer 224 is aligned with the corresponding insulating matrix212. The footprint of each magnetic layer 226 may also substantiallymatch the footprint of the adjoining magnetic seed island 214.Consequently, the placement and shape of the magnetic layers 226 may bebased at least in part on the patterned seed layer 210. Thus, thepatterned seed layer 210 has provided a growth template for the magneticlayers 226. These magnetic layers 226 may form all or part of a bottomlayer of the magnetic junctions being fabricated. In some embodiments,this layer 226 is all or part of the pinned layer. In an alternateembodiment, this magnetic layer 226 may be all or part of the freelayer.

The additional portion 224 of the magnetoresistive stack 220 is shown asunchanged in FIG. 4. However, if the additional portion 224 of themagnetoresistive stack 220 includes magnetic segregating layer(s), thenthe constituents of these layers may segregate as described above.

Fabrication of the magnetic device 200 is then completed, via step 108.Step 108 may include patterning the layer 224, providing additionallayer(s), patterning one or more of these layer(s) and providingadditional components for the magnetic device 200.

FIG. 5 depicts the magnetic device 200 after at least part of step 108has been performed. Thus, the layer 224 may have been patterned andrefilled. The layer 224 may have been segregated via the anneal in step106 and/or through an additional anneal. Thus, portions 224-1 and 224-2of the stack 220 are shown. Portions 224-1 may form part of theinsulator surrounding the sides of the regions 224-2. The portions 224-2may form the remaining part of each magnetic junction 230. Thus,portions 224-2 may include a nonmagnetic spacer layer such as atunneling barrier layer and a free layer if the magnetic layer 226 is apinned layer. Alternatively, the portions 224-2 may include anonmagnetic spacer layer such as a tunneling barrier layer and a pinnedlayer if the magnetic layer 226 is the free layer. In some cases, theportions 224-2 may also include an additional nonmagnetic layer such asan additional tunneling barrier layer and an additional pinned layer ifa dual magnetic junction is being fabricated. The nonmagnetic spacerlayer need not be patterned if it is insulating. In addition, theportions 224-2 may include magnetic segregating layers that arefabricated similar to the magnetic layers 226/insulator layers 228.Moreover, the magnetic layer 226 may form only part of the pinned orfree layer. In some embodiments, Consequently, the method 100 may form abottom pinned magnetic junction (at least part of the pinned layerclosest to the substrate 201 and formed by magnetic layer 226), a toppinned magnetic junction (at least part of the free layer closest to thesubstrate 201 and formed by magnetic layer 226), a dual magneticjunction (at least part of the lower pinned layer closest to thesubstrate 201 and formed by magnetic layer 226). Thus, the magneticjunctions 230 may be formed. In addition, electrodes, insulators,conductive lines and/or other structures may be provided.

Because the magnetic layers 226 are formed via an anneal and tend toalign with the magnetic seed islands 214, the magnetic layers 226 areself-assembled. Consequently, the magnetic layers 226 need not beseparately defined via a removal process such as RIE or ion milling.Instead, the shape, size and location of the magnetic layers 226 may bedetermined by the shape, size and location of the magnetic seed islands214. These islands 214 may be patterned prior to deposition of anyportion of the magnetoresistive stack 220. As a result, the distancebetween the magnetic layers 226 can be made small. Because the remainingportions 224-2 of the magnetic junctions 230 are thinner, any removalprocesses used in defining the remaining portions 224-2 may be for loweraspect ratios. Thus, the remaining portions 224-2 may be better able tobe defined at higher areal densities. Further, if only one magneticlayer, such as a free layer, is present in the portions 224-2, then asingle RIE etch chemistry and/or a single, short ion mill may be used.The magnetic junctions 230 may be more easily fabricated at smallersizes and smaller spacings. Fabrication of a magnetic device 200 havinghigher areal density of magnetic junctions 230 may thus be achievedusing the method 100.

FIG. 6 is a flow chart depicting an exemplary embodiment of a method 120for providing self-assembled magnetic junctions programmable using spintransfer torque. The magnetic junctions provided may be usable inmagnetic devices such as a STT-MRAM and, therefore, in a variety ofelectronic devices. Each of the magnetic junctions formed using themethod 120 includes at least a free layer having a changeable magneticmoment, a pinned layer and a nonmagnetic spacer layer such as acrystalline MgO layer. The free and/or pinned layers of the magneticjunction may have a high perpendicular magnetic anisotropy (PMA). Stateddifferently, the perpendicular magnetic anisotropy energy may exceed theout-of-plane demagnetization energy. Such a configuration allows for themagnetic moment of a high PMA layer to be stable perpendicular to plane.Additional layers including but not limited to polarization enhancementlayers (PELs), other seed layer(s) and capping layer(s) may also beprovided.

FIGS. 7-13 depict side views of exemplary embodiments of magneticdevices 250 and 250A during fabrication using the method 120. In someembodiments, the magnetic devices 250 and 250A are STT-MRAMs. FIGS. 7-13are not to scale and only structures of interest are separately labeledand included. Referring to FIGS. 6-13, the method 120 is described inthe context of the magnetic devices 250 and 250A including particularmagnetic junctions. However, other magnetic devices including othermagnetic junction(s) may be formed. Further, the method 120 may startafter other steps in forming the magnetic device 250/250A have beenperformed. For example, selection transistor(s), contacts, or othercomponents may have been fabricated. For simplicity, some steps may beomitted, performed in another order, include substeps and/or combined.

A patterned seed layer is provided, via step 122. The patterned seedlayer includes magnetic seed islands interspersed with an insulator.Step 122 is analogous to step 102 of the method 100. FIG. 7 depicts themagnetic device 250 after step 122 has been performed. The patternedseed layer 260 has been provided on the substrate 251. Selectiontransistors 252 and conductive vias 254 have also been formed prior tothe patterned seed layer 260. The seed layer 260 includes magnetic seedislands 264 interspersed with an insulating matrix 262. Although onlyone dimension in the plane of the layers is shown (e.g. left-right), thepatterned seed layer 260 is typically patterned in two dimensions. Thepatterned seed layer 260, magnetic seed islands 264 and insulatingmatrix 262 are analogous to patterned seed layer 210, magnetic seedislands 214 and insulating matrix 212, respectively. Consequently, thediscussion above with respect to the patterned seed layer 210 isapplicable to the patterned seed layer 260. The magnetic seed islands264 may include one or more of CrV, NiTa, RuAl, TiN, CrTi and/or otherappropriate materials. For example, the insulating matrix 262 may besilicon oxide, such as SiO₂ and the magnetic seed islands 264 areappropriate for the magnetic layer to be formed. Other insulatingmatrices may include but are not limited to AlO, AlN, SiO, SiN, MgO, MgNand TiO. The magnetic seed islands 264 are shown as having length l1,while the insulating matrix has length l2. In the embodiment shown, l2is less than l1 (l2<l1). However, in other embodiments, otherrelationships may hold.

A magnetic segregating layer is provided, via step 124. A magneticsegregating layer includes at least one magnetic material and at leastone insulator that are immiscible. For example, the magnetic materialmay be FePt and/or CoPt. The insulator might be SiO₂, alumina, B₂O₃, AlNand/or MgO. Other combinations of magnetic material(s) and/orinsulator(s) might be used. Step 124 may include sputtering or otherwisedepositing these materials such that the resulting film is metastable.Step 124 is thus analogous to at least part or step 104. FIG. 8 depictsthe magnetic device 250 after step 124 is performed. A magneticsegregating layer 270 has been deposited on the patterned seed layer210. The magnetic segregating layer 270 may share an interface with thepatterned seed layer 260. The magnetic segregating layer 270 may beanalogous to the magnetic segregating layer 222 discussed above.Although shown as a single layer, the magnetic segregating layer 270 mayinclude multiple sublayers. The stoichiometry of the magneticsegregating layer 270 may depend upon the size of the magnetic junctionsin the plane perpendicular to the side view shown as well as thedistance desired between the magnetic junctions.

The magnetic segregating layer 270 is annealed so that its constituentssegregate, via step 126. In various embodiments, the anneal may beaccomplished via block heating or via RTA. In some embodiments, theanneal is at temperatures of at least two hundred degrees Celsius andnot more than seven hundred degrees Celsius. In some embodiments, theannealing temperature may be compatible with semiconductor processes,for example nominally four hundred degrees Celsius. For an RTA, theanneal time may be at least one and not more than three thousandseconds. The annealing time for block heating may be on the order of atleast one hundred seconds and not more than two hours. However, theannealing process is desired to take into account the underlyingtransistor temperature tolerance, through-via chip bonding technology,the magnetic properties of the junction and/or other factors. Thus,other temperatures and/or times are possible. The magnetic material(s)in the magnetic segregating layer 270 separate from the insulator. Themagnetic material(s) thus tend to form islands. Because of the presenceof the magnetic seed islands 264, the magnetic material(s) tend to alignwith and share at least part of an interface with the magnetic seedislands 264. Similarly, the insulator tends to align with the insulatingmatrix 262. In an alternate embodiment, the nonmagnetic spacer layer mayalso be provided in step 124 and undergo an anneal in step 126.

FIG. 9 depicts the magnetic device 250 after step 126 has beenperformed. Thus, the magnetic segregating layer 270 has separated intomagnetic layers 274 and insulator layers 272 that are aligned with themagnetic seed islands 264 and insulating matrix 262, respectively. Themagnetic layers 274 may but need not be centered over the magnetic seedislands 264 and may but need not be the same size as the islands 264.Similarly, the insulating layers 272 may but need not be centered overthe insulating matrix 2612 and may but need not be the same size as theinsulating matrix 262. The magnetic layers 274 have length l3. In theembodiment shown, the magnetic layers 274 are longer than the magneticseed islands (l3>l1). However, in other embodiments, there may be otherrelationships between the lengths and/or depths perpendicular to theplane of the page. Thus, each magnetic layer 274 is aligned with amagnetic seed island 264, where alignment is defined above. Similarly,each insulator layer 272 is aligned with the corresponding insulatingmatrix 262. The footprint of each magnetic layer 274 may alsosubstantially match the footprint of the adjoining magnetic seed island264. Consequently, the placement and shape of the magnetic layers 274may be based at least in part on the patterned seed layer 260. Thepatterned seed layer 260 has provided a growth template for the magneticlayers 274. These magnetic layers 274 may form all or part of a bottomlayer of the magnetic junctions being fabricated. In some embodiments,this layer 274 magnetic is all or part of the pinned layer. In analternate embodiment, this magnetic layer 274 may be all or part of thefree layer.

The remaining layers of the magnetoresistive stack are deposited, viastep 128. These layers may include but not be limited to the layer(s)for the nonmagnetic spacer layer and the free layer. Alternatively, thelayers may be the nonmagnetic spacer layer and pinned layer. However, ingeneral, it is preferred to have the free layer definedphotolithographically for improved control over the dimensions and shapeof the free layer. Thus, in some embodiments the magnetic layersdeposited in step 128 are part of the free layer. The top electrode maybe provided, via step 130. Step 130 may include depositing the layer forthe top electrode and photolithographically defining the top electrodes.

FIG. 10 depicts the magnetic device 250 after step 130 has beenperformed. Thus, the nonmagnetic spacer layer 276 and layer(s) for thefree layer or pinned layer 278 have been provided in step 128. Thenonmagnetic spacer layer 276 may be an MgO tunneling barrier layer.Thus, step 128 may include depositing an Mg layer and then oxidizing theMg layer. Alternatively, an MgO layer may be deposited directly. In someembodiments, an anneal may be performed in order to improvecrystallization of the MgO layer. The magnetic layer(s) 278 may be asingle layer or a multilayer. The magnetic layer(s) 278 might form a SAFor may be another structure. The magnetic layer(s) 278 might include aPEL and/or other layers. The electrodes 275 are also shown. Theelectrodes have length l4. In the embodiment shown, the electrodes areshorter than the magnetic layers 274 (l4<l3). However, otherrelationships between the lengths are possible. Although the mask usedin fabricating the electrodes 275 is not shown, in other embodiments themask may be present.

The sides of the magnetic junctions are defined, via step 132. Step 132include defining the edges of at least the magnetic layer(s) such as thefree layer. In some embodiments, the nonmagnetic spacer layer is alsodefined. However, in embodiments in which the nonmagnetic spacer layeris a tunneling barrier layer, the edges of the nonmagnetic spacer layermight not be defined. In some embodiments, the electrode provided instep 130 and the mask used in providing the electrode may be used instep 132 to photolithographically define the edges of the magneticjunction. For example, a short ion mill and/or RIE may be performed toremove exposed portions of the magnetic layer(s) provided in step 128.

FIG. 11 depicts the magnetic device 250 after step 132 has beenperformed. In the embodiment shown, the magnetic layers 278′ remain.Thus, the ion mill, RIE or other removal process has not removed all ofthe nonmagnetic spacer layer 276. Although shown as though the entirelayer is present, in some embodiments, the process used to removeexposed portions of the magnetic layer(s) 278 may remove some or all ofthe exposed portions of the nonmagnetic spacer layer 276. As discussedabove, the layers 278′ may be free layers while the magnetic layers 274may be pinned layers. Alternatively, the layers 278′ and 274 may bepinned and free layers, respectively. For the reasons described above,it may be desirable for the layer 278 to be a free layer. Thus, themagnetic device 250 is fabricated.

FIGS. 12-13 depicts an alternate embodiment of a magnetic device 250A inwhich step 128 deposits not only nonmagnetic spacer layer 276 and freelayer 278 but also an additional nonmagnetic spacer layer 277A and anadditional pinned layer 279A. The magnetic device 250A is analogous tothe magnetic device 250. Consequently, similar components have analogouslabels. FIG. 12 depicts the magnetic device 250A after step 130. Thus,the electrodes 275 have been formed. FIG. 13 depicts the magnetic device250A after step 132 is performed. Thus, the free layer 278A, additionalnonmagnetic spacer layer 277A and additional pinned layer 279A have beendefined. Although shown as continuous, in some embodiments, step 132might include removing an exposed portion of the nonmagnetic spacerlayer 276. Consequently, dual magnetic junctions 280A have been formed.

The magnetic junctions 280 and/or 280A are formed using the method 120.The magnetic junction 280/280A may include a pinned layer 274, anonmagnetic spacer layer 276 and free layer 278. Alternatively, the freelayer might be formed by the magnetic layer 274 and the pinned layerformed with layer 278′. In some embodiments, a dual magnetic junction280A may be formed. In such embodiments, the magnetic layer 274 is apinned layer. The ensuing discussion assumes the magnetic layer 274 isthe pinned layer. However, an analogous discussion holds if the freelayer is the magnetic layer 274. The pinned layers 274 are formed via ananneal and tend to align with the magnetic seed islands 264. Thus, thepinned layers 274 are self-assembled. Consequently, the pinned layers274 need not be separately defined via a removal process such as RIE orion milling. Thus, only the free layer 278′ or only the layers 278A,277A and 279A may be patterned in step 132. Removal processes for highaspect ratio components may be reduced or avoided. As a result, themagnetic junctions 280 and/or 280A may be smaller and closer together.The magnetic device 200 may achieve a higher areal density. In addition,because only the free layer 278′ may be defined in step 132, a singleRIE chemistry or short ion mill may be used. Fabrication of a higherareal density magnetic device 250/250A may be facilitated.

FIG. 14 is a flow chart depicting an exemplary embodiment of a method140 for providing self-assembled magnetic junctions programmable usingspin transfer torque. The magnetic junctions provided may be usable inmagnetic devices such as a STT-MRAM and, therefore, in a variety ofelectronic devices. Each of the magnetic junctions formed using themethod 140 includes at least a free layer having a changeable magneticmoment, a pinned layer and a nonmagnetic spacer layer such as acrystalline MgO layer. The free and/or pinned layers of the magneticjunction may have a high PMA. Such a configuration allows for themagnetic moment of a high PMA layer to be stable perpendicular to plane.Additional layers including but not limited to PELs, other seed layer(s)and capping layer(s) may also be provided.

FIGS. 15-21 depict side views of exemplary embodiments of a magneticdevice 250B, 250C and 250D including magnetic junctions duringfabrication using the method 140. The magnetic devices 250B, 250C and250D are analogous to the magnetic devices 250 and 250A. Consequently,similar components have analogous labels. In some embodiments, themagnetic device 250B, 250C and 250D are each an STT-MRAM. FIGS. 15-21are not to scale and only structures of interest may be separatelylabeled and included. Referring to FIGS. 14-21, the method 140 isdescribed in the context of the magnetic devices 250B, 250C and 250D.However, other magnetic devices including other magnetic junction(s) maybe formed. Further, the method 120 may start after other steps informing the magnetic device 250B/250C/250D have been performed. Forexample, selection transistor(s), contacts, or other components may havebeen fabricated. For simplicity, some steps may be omitted, performed inanother order, include substeps and/or combined.

A patterned seed layer is provided, via step 142. The patterned seedlayer includes magnetic seed islands interspersed with an insulator.Step 142 is analogous to step 102 of the method 100 and to step 122 ofthe method 120. FIG. 15 depicts the magnetic device 250B after step 142has been performed. The magnetic device 250B is analogous to themagnetic device(s) 250 and/or 250A. Consequently, similar componentshave analogous labels. The patterned seed layer 260 has been provided onthe substrate 251. Selection transistors 252 and conductive vias 254have also been formed prior to the patterned seed layer 260. The seedlayer 260 includes magnetic seed islands 264 interspersed with aninsulating matrix 262. The patterned seed layer 260, magnetic seedislands 264 and insulating matrix 262 are analogous to patterned seedlayer 210, magnetic seed islands 214 and insulating matrix 212,respectively. Consequently, the discussion above with respect to thepatterned seed layers 210 and 260 is applicable to the patterned seedlayers 260 of the devices 250B, 250C and 250D. For example, theinsulating matrix 262 may be silicon oxide, such as SiO₂, AlO, AlN, SiO,SiN, MgO, MgN and/or TiO. The magnetic seed islands 264 are appropriatefor the magnetic layer to be formed. The magnetic seed islands 264 mayinclude CrV, NiTa, RuAl, TiN, CrTi and/or other appropriate material(s).The magnetic seed islands 264 are shown as having length l1, while theinsulating matrix has length l2. In the embodiment shown, l2 is lessthan l1 (l2<l1). However, in other embodiments, other relationships mayhold.

At least part of a magnetoresistive stack including at least twomagnetic segregating layers is provided, via step 144. A magneticsegregating layer includes at least one magnetic material and at leastone insulator that are immiscible. For example, the magnetic materialmay be FePt and/or CoPt. In some embodiments, CoFeB might be used. Theinsulator might be SiO₂, alumina, B₂O₃, AlN and/or MgO. Othercombinations of magnetic material(s) and/or insulator(s) might be used.The magnetic materials in one magnetic segregating layer provided instep 144 can but need not be the same as the magnetic material(s) in theother of the two magnetic segregating layers. Similarly, the insulatorin one magnetic segregating layer can but need not be the same as theinsulator(s) in the other of the two magnetic segregating layers. Step144 may include sputtering or otherwise depositing these materials suchthat each resulting film is metastable. In addition, the nonmagneticand/or other layer(s) between the magnetic segregation layers may bedeposited as part of step 144.

FIG. 15 depicts the magnetic device 250B after step 144 is performed. Afirst magnetic segregating layer 270 has been deposited on the patternedseed layer 210. The magnetic segregating layer 270 may share aninterface with the patterned seed layer 260. The magnetic segregatinglayer 270 may be analogous to the magnetic segregating layer 222discussed above. Although shown as a single layer, the magneticsegregating layer 270 may include multiple sublayers. The stoichiometryof the magnetic segregating layer 270 may depend upon the size of themagnetic junctions in the plane perpendicular to the side view shown aswell as the distance desired between the magnetic junctions. Also shownis the nonmagnetic spacer layer 276B and another magnetic segregatinglayer 278B. The magnetic segregating layer 278B is analogous to thelayer 270. In some embodiments, the magnetic segregating layer 270 maybe used for the pinned layer while the magnetic segregating layer 278Bmay be used for the free layer of each magnetic junction. Alternatively,the magnetic segregating layer 270 may be used for the free layer whilethe magnetic segregating layer 278B may be used for the pinned layer ofeach magnetic junction.

The magnetic segregating layers 270 and 278B are annealed so that theconstituents of each layer segregate, via step 146. The anneal may beaccomplished via a block anneal or an RTA. For example, the annealtemperatures may be at least two hundred degrees Celsius and not morethan seven hundred degrees Celsius. For a block anneal the anneal timemay be at least one hundred seconds and not more than two hours. For anRTA the anneal time may be at least one second and not more threethousand seconds. As discussed above, various factors may be taken intoaccount. Thus, the time and/or temperature of the anneal may differ. Themagnetic material(s) in the magnetic segregating layers 270 and 278Bseparate from the insulator. FIG. 16 depicts the magnetic device 250Bafter step 146 is performed. The magnetic material(s) thus tend to formislands. Because of the presence of the magnetic seed islands 264, themagnetic material(s) in the layer 270 tend to align with and share atleast part of an interface with the magnetic seed islands 264.Similarly, the insulator 272 tends to align with the insulating matrix262. Stated differently, crystal grain growth is promoted by atomiclattice crystallization. So, alignment of the multiple layers 264, 274and 278B-1 and layers 262, 272 and 278B-2 occurs because of the grainsegregation. This alignment is promoted by ensuring amount of theinsulator in each layer 270 and 278 allows the grains to be of the samesize. The footprint of each magnetic layer 274 may also substantiallymatch the footprint of the adjoining magnetic seed island 264.Consequently, the patterned seed layer 260 has provided a growthtemplate for the magnetic layers 274. These magnetic layers 274 may formall or part of a bottom layer of the magnetic junctions beingfabricated. In some embodiments, this layer 274 magnetic is all or partof the pinned layer. In an alternate embodiment, this magnetic layer 274may be all or part of the free layer. Similarly, the magnetic materials278B-1 in the magnetic segregating layer 278B tend to align with themagnetic materials 274. The insulator 278B-2 tends to align with theinsulator 272. For simplicity, only one region of the insulator 278B-2is labeled.

The remaining layers of the magnetoresistive stack, if any, aredeposited, via step 148. For the magnetic device 250B, there are noadditional layers. The top electrode may be provided, via step 150. Step150 may include depositing the layer for the top electrode andphotolithographically defining the top electrodes.

FIG. 17 depicts the magnetic device 250B after step 150 has beenperformed. Thus, the electrodes 275B are shown. In some embodiments, themagnetic layers 274 are the pinned layer and the magnetic layer 278B-1are the free layer for each magnetic junction 280B. Alternatively, themagnetic layers 274 are the free layer and the magnetic layer 278B-1 arethe pinned layer for each magnetic junction 280B.

Any remaining layers are optionally provided and defined, via step 152.Step 152 may be used if a dual magnetic junction is being provided. Insome embodiments, step 152 is performed before step 150. Step 152 may beomitted for the magnetic device 250B. However, for the magnetic devices250C and 250D, discussed below, step 152 may be performed.

FIG. 18 depicts the magnetic device 250C during step 152. In FIG. 18,additional layers 277C and 279C have been deposited. These layers forman additional nonmagnetic spacer layer and an additional pinned layer ina dual magnetic junction. FIG. 19 depicts the magnetic device 250C afterthe upper layers have been defined in step 152 and the electrodes 275Chave been provided. Thus, the additional nonmagnetic spacer layer 277Cand additional pinned layer 279C have been provided. FIGS. 20 and 21depict an alternate embodiment of the magnetic device 250D. FIG. 20depicts the magnetic device 250D during step 152. Thus, layers 277D and279D for the additional nonmagnetic spacer layer and additional pinnedlayer in a dual structure are shown. The layer 279D is another magneticsegregating layer. FIG. 21 depicts the magnetic device 250D after step152 is completed. Thus, an anneal has been performed such that themagnetic segregation layer 279D has segregated into magnetic layer279D-1 and insulator layer 279D-2. Only one instance of the insulator279D-2 is labeled for clarity. The magnetic layers 279D-1 may align withthe remaining magnetic layers 278D-1 and 274. Similarly, the insulatorlayers 279D-2 may align with the remaining insulator layers 278D-2 and272.

The magnetic junctions 280B, 280C and/or 280D are formed using themethod 140. The magnetic junction 280B/280C/280D may include a pinnedlayer 274, a nonmagnetic spacer layer 276 and free layer 278B-1.Alternatively, the free layer might be formed by the magnetic layer 274and the pinned layer formed with layer 278B-1. For the dual structures,the additional pinned layers are formed from magnetic layers 279C-1 and279D-1.

The magnetic devices 250B, 250C and 250D may share the benefits of themagnetic devices 250 and 250A. Removal processes for high aspect ratiocomponents may be avoided. In addition, a single etch chemistry may beused in defining at least some of the layers such as layer 279C. As aresult, the magnetic junctions 280B, 280C and/or 280D may be fabricatedto be smaller and closer together. The magnetic device 250B, 250C and/or250D maybe achieve a higher areal density. Fabrication may be improvedfor a higher density magnetic device 250/250A.

Although the method and apparatus have been described in the context ofspecific features, steps and components, one of ordinary skill in theart will recognize that one or more of these features, steps and/orcomponents may be combined in other manners not inconsistent with thedescription herein.

FIG. 22 depicts an exemplary embodiment of a memory 300 that may use oneor more of the magnetic junctions 230, 280, 280A, 280B, 280C, 280Dand/or other magnetic junction(s) formed in accordance with the methodsdescribed herein. The magnetic memory 300 includes reading/writingcolumn select drivers 302 and 306 as well as word line select driver304. Note that other and/or different components may be provided. Thestorage region of the memory 300 includes magnetic storage cells 310.Each magnetic storage cell includes at least one magnetic junction 312and at least one selection device 314. In some embodiments, theselection device 314 is a transistor. The magnetic junctions 312 may beone of the magnetic junctions 230, 280, 280A, 280B, 280C, 280D and/orother magnetic junction(s) formed as disclosed herein. Although onemagnetic junction 312 is shown per cell 310, in other embodiments,another number of magnetic junctions 312 may be provided per cell. Assuch, the magnetic memory 300 may enjoy the benefits described above.

A method and system for providing a magnetic junction and a memoryfabricated using the magnetic junction has been described. The methodand system have been described in accordance with the exemplaryembodiments shown, and one of ordinary skill in the art will readilyrecognize that there could be variations to the embodiments, and anyvariations would be within the spirit and scope of the method andsystem. Accordingly, many modifications may be made by one of ordinaryskill in the art without departing from the spirit and scope of theappended claims.

1. A method for providing a plurality of magnetic junctions on asubstrate and usable in a magnetic device, the method comprising:providing a patterned seed layer, the patterned seed layer including aplurality of magnetic seed islands interspersed with an insulatingmatrix; providing at least a portion of a magnetoresistive stack afterthe step of providing the patterned seed layer, the magnetoresistivestack including at least one magnetic segregating layer, the at leastone magnetic segregating layer including at least one magnetic materialand at least one insulator; annealing the at least the portion of themagnetoresistive stack such that the at least one magnetic segregatinglayer segregates such that a plurality of portions of at least onemagnetic material align with the plurality of magnetic seed islands andsuch that a plurality of portions of the at least one insulator alignwith the insulating matrix.
 2. The method of claim 1 wherein each of theplurality of the magnetic junctions includes a pinned layer, anonmagnetic spacer layer and a free layer, the nonmagnetic spacer layerbeing between the pinned layer and the free layer, a portion theplurality of portions of the at least one magnetic material aligned withthe plurality of magnetic seed islands forming one of the pinned layerand the free layer, the method further including: providing a remainingportion of the magnetoresistive stack, the remaining portion of themagnetoresistive stack including a first layer for the nonmagneticspacer layer and a second layer for an other of the pinned layer and thefree layer.
 3. The method of claim 2 further comprising: defining atleast the other of the pinned layer and the free layer from theremaining portion of the magnetoresistive stack.
 4. The method of claim2 further comprising: providing a patterned top electrode layerincluding a plurality of electrodes aligned with the plurality ofmagnetic seed islands; and defining at least the other of the pinnedlayer and the free layer from the remaining portion of themagnetoresistive stack after the step of providing the patterned topelectrode layer.
 5. The method of claim 2 wherein the each of theplurality of magnetic junctions further includes an additional pinnedlayer and an additional nonmagnetic spacer layer, the additionalnonmagnetic spacer layer being between the additional pinned layer andthe free layer, wherein the magnetoresistive stack further includes athird layer for the additional nonmagnetic spacer layer and a fourthlayer for the additional pinned layer, and wherein the method furtherincludes defining at least the free layer and the additional pinnedlayer from the remaining portion of the magnetoresistive stack.
 6. Themethod of claim 1 wherein each of the plurality of the magneticjunctions includes a pinned layer, a nonmagnetic spacer layer and a freelayer, the nonmagnetic spacer layer being between the pinned layer andthe free layer, a portion the plurality of portions of the at least onemagnetic material aligned with the plurality of magnetic seed islandsforming one of the pinned layer and the free layer, wherein the step ofproviding the at least the portion of the magnetoresistive stack furtherincludes: providing a first layer for the nonmagnetic spacer layer;providing at least one additional segregating layer for an other of thepinned layer and the free layer, the at least one additional segregatinglayer including at least one additional magnetic material and at leastone additional insulator, the at least one additional segregating layersegregating due to the step of providing the anneal such that aplurality of portions of the at least one additional magnetic materialalign with the plurality of portions of the at least one magneticmaterial for the plurality of magnetic junctions, a portion of theplurality of portions of the at least one additional magnetic materialforming the other of the pinned layer and the free layer.
 7. The methodof claim 6 further comprising: providing a plurality of electrodesaligned with the free layer.
 8. The method of claim 1 wherein the atleast one magnetic material includes at least one of FePt and CoPt andwherein the insulating matrix includes at least one of silicon oxide andaluminum oxide.
 9. A method for providing a plurality of magneticjunctions residing on a substrate, each of the plurality of magneticjunctions including a pinned layer, a free layer and a nonmagneticspacer layer between the pinned layer and the free layer, the methodcomprising: providing a patterned seed layer, the patterned seed layerincluding a plurality of magnetic seed islands interspersed with aninsulating matrix; depositing a magnetic segregating layer, the magneticsegregating layer including a magnetic alloy and an insulator, themagnetic alloy including at least one of FePt and CoPt, the insulatorbeing selected from silicon oxide aluminum oxide; performing an annealto segregate the magnetic segregating layer such that a plurality ofportions of the magnetic material align with the plurality of magneticseed islands and such that a plurality of portions of the insulatoralign with the insulating matrix, the plurality of portions of themagnetic material forming the pinned layer for the each of the pluralityof magnetic junctions.
 10. A memory magnetic comprising: a patternedseed layer including a plurality of magnetic seed islands interspersedwith an insulating matrix; a plurality of magnetic storage cells, eachof the plurality of magnetic storage cells including at least onemagnetic junction aligned with the plurality of magnetic seed islands,the at least one magnetic junction including a free layer, a nonmagneticspacer layer and a pinned layer, one of the pinned layer and the freelayer being formed from at least one magnetic segregating layerincluding at least one magnetic material and at least one insulator, theat least one magnetic segregating layer being segregated such that aplurality of portions of the at least one magnetic material align withthe magnetic seed islands and such that a plurality of portions of theat least one insulator align with the insulating matrix, a portion ofthe plurality of portions of the at least one magnetic material formingthe one of the pinned layer and the free layer; and a plurality of bitlines coupled with the plurality of magnetic storage cells.
 11. Themagnetic memory of claim 10 wherein each of the at least one magneticjunction further includes an additional nonmagnetic spacer layer and anadditional pinned layer, the additional nonmagnetic spacer layer beingbetween the free layer and the additional pinned layer.
 12. The magneticmemory of claim 10 wherein the at least one magnetic material includesat least one of FePt and CoPt and wherein the at least one insulatorincludes at least one of silicon oxide and aluminum oxide.
 13. Themagnetic memory of claim 10 wherein an other of the pinned layer and thefree layer is formed from at least one additional magnetic segregatinglayer, the at least one additional magnetic segregating layer includingat least one additional magnetic material and at least one additionalinsulator, the at least one additional magnetic segregating layer beingsegregated such that a plurality of portions of at least one additionalmagnetic material align with the magnetic seed islands and such that aplurality of portions of the at least one additional insulator alignwith the insulating matrix, a portion of the plurality of portions ofthe at least one additional magnetic material forming the other of thepinned layer and the free layer.
 14. The magnetic memory of claim 13wherein the at least one additional magnetic material includes at leastone of FePt and CoPt and wherein the at least one additional insulatorincludes at least one of silicon oxide and aluminum oxide.
 15. Themagnetic memory of claim 10 wherein the at least one magnetic materialincludes at least one of FePt and CoPt and wherein the insulating matrixincludes at least one of silicon oxide and aluminum oxide.